Crude oils and fuel oils of improved pour point depressant and flowability properties

ABSTRACT

1. PETROLEUM CRUDE OIL AND FUEL OIL COMPOSITIONS HAVING IMPROVED POUR AND FLOWABILITY CHARACTERISTICS AT LOW TEMPERATURES, COMPRISING A PETROLEUM OIL OF THE GROUP CONSISTING OF A CRUDE OIL AND A FUEL OIL NORMALLY HAVING UNDESIRABLE POUR AND FLOWABILITY CHARACTERISTICS AT LOW TEMPERATURE, AND FROM ABOUT 0.001% TO ABOUT 5% OF A HYDROLYZED COPOLYMER OF ETHYLENE AND A VINYL ESTER OF A LOWER ALKYL FATTY ACID HAVING UP TO FIVE CARBON ATOMS, SAID COPOLYMER HAVING AN AVERAGE MOLECULAR WEIGHT OF FROM ABOUT 500 TO ABOUT 30,000, AND CONTAINING ABOUT 10-90% ETHYLENE AND ABOUT 90-10% OF SAID VINYL ESTER, SAID COPOLYMER BEING HYDROLYZED TO THE EXTEND OFF HYDROLYZING FROM ABOUT 10% TO ABOUT 90% OF THE ESTER UNITS OF SAID COPOLYMER.

United States Patent 3,846,092 CRUDE OILS AND FUEL OILS OF IMPROVED POURPOINT DEPRESSANT AND FLOWABILITY PROPERTIES Peter G. Pappas, DownersGrove, Walter C. Edmisten, Olympia Fields, and Hobe Schroeder vonLevern, Downers Grove, Ill., assiguors to Standard Oil Company, Chicago,Ill. No Drawing. Filed Mar. 21, 1973, Ser. No. 343,286

Int. Cl. C101 1/16 U.S. Cl. 44-62 8 Claims ABSTRACT OF THE DISCLOSUREHydrocarbon fuel oils having improved pour and flowabilitycharacteristics at temperatures at which such characteristics of suchfuel oils are adversely affected, are obtained by incorporating in suchhydrocarbon fuel oils small amounts, i.e., from about 0.001% to aboutpreferably from about 0.0025% to about 1.0%, of a A BACKGROUND OF THEINVENTION In the storage, transportation and use of hydrocarbon fueloils, problems associated with the pour point of such fuels have beenlong recognized. The pour point of an oil is defined as the lowesttemperature at which the oil will flow when chilled without disturbanceunder specified conditions. Pour point problems arise through theformation of solid or semi-solid waxy particles in the fuel oil, e.g.,distillate fuel oils, such as heating oils, diesel oils, turbo-jet fuelsand the like, when such fuel oils are subjected to low temperatures instorage. A related problem also exists in respect of hydrocarbon residfuel oils and waxy crude oils, in which the waxy components of such oilsadversely affect the flowability and/or pumpability of the oil under lowtemperature conditions.

The formation of such solid or semi-solid waxy particles in fuel oilsand in waxy crude oils at temperatures just below their pour pointcauses serious distribution and/or operating difficulties. For example,the distribution of such oils by pumping is rendered difiicult orimpossible at temperatures below the pour point of the oil; also, theflow of the oil at such temperatures through filters in heating systemscannot be maintained, resulting in the failure of the equipment tofunction. The formation of solid or semi-solid Waxy particles inwax-containing crude oils gives rise to difficulties in the movement ofsuch crude oils through pipelines at low ambient temperatures.

In respect of fuel oils, the aforementioned problems have been in partremedied by lowering the end points of oils used for blending heatingand diesel oils. It has also been suggested that the fuel oils,particularly distillate fuel oils, may be dewaxed such as by ureadewaxing. However, readjustment of end points causes a loss of valuableproduct as blending material for fuel oil stocks; also, dewaxingoperations are costly.

Another approach in overcoming the problem has been to attempt to find apour point depressant which will lower the pour point of the fuel oil orcrude oil as is known to be done in lowering the pour point oflubricating oils. However, materials which are effective in lowering thepour point of lubricating oils are ineffective as pour point depressantsfor fuel oils or crude oils.

Recently, certain products have been made which provide pour pointdepressant properties in certain fuel oils, particularly the distillatefuel oils. However, while such pour point depressant additives may beeffective in socalled distillate fuel oils, they generally are notsufficiently effective in resid fuel oils or in waxy crude oils. U.S.Pat. 3,048,479 issued Aug. 7, 1962 to S. Ilnyckyj et al., disclosescopolymers of ethylene and vinyl acetate as pour point depressants formiddle distillates; however, such copolymers are not sufiicientlyeffective in resid fuel oils or in crude oils. Other patents in thefield of such copolymers are illustrated by U.S. 2,499,723; U.S.2,654,188; U.S. 3,093,723; U.S. 3,126,364; U.S. 3,236,612 and others.

The state of the art is further illustrated by the following patents:U.S. 3,447,915 issued to B. Otto, June 3, 1969, teaches the use ofterpolymers of ethylene, propylene and an alkyl ester of acrylic acid ormethacrylic acid as pour point depressors in fuel oils. The pour pointdepressants and flow improvers disclosed in U.S. 3,467,597, issued to N.Tunkel et al., Sept. 16, 1969, are terpolymers of ethylene, vinylesters, e.g. vinyl acetate, and a monoolefinically unsaturatedpolymerizable compound grafted with ethylene. U.S. Pat. 3,679,380 issuedJuly 25, 1972 to C. Biswell et al. discloses middle distillate fuelcompositions containing a copolymer of ethylene, propylene and1,4-hexadiene as pour point depressants. To facilitate the movement ofwaxy crude oil through pipelines, U.S. Pat. 3,675,671 issued July 11,1972 to W. Sweeny et al., discloses such crude oils with a low pourcrude oil and a copolymer of ethylene and a vinyl fatty acid ester, suchas vinyl acetate.

We have found that by the hydrolysis of copolymers of ethylene and avinyl ester of fatty acids of up to 5- carbon atoms, the productsobtained are effective pour point depressants for hydrocarbon distillateand resid fuel oils, and are also effective in improving the flowabilityand pumpability of such fuel oils as well as wax-containing crude oils.The hydrolysis, by alcoholysis or by saponification, of copolymers ofethylene and vinyl esters is disclosed in such prior art as U.S. Pats.3,344,129; 3,386,978; 3,560,318; 3,560,461; 3,562,234, and others. Suchart neither teaches nor suggests the use of such products as pour pointdepressants or flow improvers in hydrocarbon fuel oils and/ or waxypetroleum crude oils.

SUMMARY OF THE INVENTION In accordance with the present invention,additives for fuel oils and crude oils which are effective in loweringthe pour point and in improving the flowability and/ or pumpability ofsuch oils at low temperatures, i.e., at temperatures at or below whichthe waxy components thereof start to become semi-solid or solid, areobtained by hydrolyzing copolymers of ethylene and a vinyl ester of analkyl fatty acid having up to about five carbon atoms, which copolymershave an average molecular Weight of from about 500 to about 30,000,preferably from about 700 to about 10,000, and contain from about 10% toabout preferably from about 25% to about 40% vinyl ester units. Thehydrolysis of such copolymers is conducted under conditions which willeffect the hydrolysis of from about 10% to about 90%, preferably fromabout 40% to about 70% of the vinyl ester units of the copolymer.

Preparation of the copolymer Methods of preparing the starting copolymerof ethylene and the vinyl ester, e.g., the vinyl acetate, are well knownin the art. Such copolymers can be produced by the copolymerization ofethylene with the vinyl ester under pressure at elevated temperatures,i.e. from about 280 F. to about 350 F. in the presence of a free radicalcatalyst, such as a peroxy compound. Processes for the preparation ofsuch copolymers are described in US. Pats. 2,396,785 and 3,048,479.

In US. Pat. 3,048,479, ethylene vinyl acetate polymers are prepared in abenzene solution using di-tertiary-butylperoxide, as the catalyst, at atemperature of 280-340 F and at a pressure of 7002,000 pounds. Afterpurging the reactor with nitrogen and ethylene, the vinyl acetate,solvent and catalyst are introduced into the reactor, the sufficientethylene charged to the reactor to yield the desired pressure at thereaction temperature. Additional ethylene is added during thepolymerization to maintain the desired pressure in the reactor. Thepolymerization is considered complete, when a pressure drop of less than50 p.s.i.g. per hour is observed, The product is then stripped freeunder vacuum of solids and unreacted vinyl acetate.

Preparation of hydrolyzed copolymer The said copolymers may behydrolyzed by alcoholysis or by saponification. Such methods are wellknown in the art, as exemplified by U.S. lPats. Nos. 3,344,129;3,386,978; 3,560,318; 3,560,461; 3,562,234 and others. Illustrative of amethod of hydrolyzing the ethylene-vinyl ester copolymer is thefollowing: The hydrolysis of the copolymer is carried out underanhydrous conditions by heating the copolymer, preferably diluted toabout 2060%, in an inert diluent or solvent, such as for example,kerosene, naphtha, etc., or an aromatic hydrocarbon solvent, e.g.toluene, to reflux temperature while purging with dry nitrogen or otherinert gas, then cooling down to a temperature of from about 120 C. toabout 50 C., preferably 70 C., while continuing blowing with the inertgas, such as nitrogen. From about 0.23 to about 1 mole, based on thecopolymer, of an anhydrus lower alkanol, e.g. methanol, ethanol, areadded, and the reaction temperature raised to reflux temperature. Atthis point there is rapidly added as the catalyst from about 0.005 toabout 0.1 mole of sodium methoxide or sodium ethoxide (depending uponthe alkanol employed). The catalyst can be used in solutions of fromabout 0.1 N to about 10 N, preferably about 1 N. After the catalyst hasbeen added the reaction mixture temperature is raised to refluxtemperature, and maintained at such temperature for about 0.1-3 hours,preferably about 1 hour, while stirring the reaction mass. At

the end of the reaction period the reaction is quenched by adding to thereactor from about 0.005 to about 0.1 mole of the lower alkyl fatty acidcorresponding to the vinyl ester, e.g. acetic acid when the vinyl esteris vinyl acetate, and the reaction mass stirred for about 5-10 minutes.The quenched reaction mixture is then heated to a temperature of about120 C.150 C. to strip off volatiles, such as alkanol, alkyl ester of thelower fatty acid, and diluent or solvent light ends.

The hydrolyzed copolymers of the present invention are effective inpetroleum distillate and residual fuel oils, and in petroleum crudeoils. The fuel oil, such as for example, heavy industrial residualfuels, e.g. Bunker C fuel, and crude oils. The fuel oil may be virgin orcracked petroleum stock, or mixtures thereof, boiling in the range offrom about 200 F. to about 750 F., and preferably in the range of about350 F. to 750 F. The fuel oil may contain other additives such as, forexample, rust inhibitors, corrosion inhibitors, antitoxidants,detergents etc.

The additives of the present invention are used in the fuel oils andcrude oils in amounts of from about 0.001% to about 5%, preferably fromabout 0.0025% to about 1.0%. The additives, may for convenience, beprepared as addition agent concentrates. Accordingly, the hydrolyzedcopolymer may be dissolved in a suitable organic solvent therefor inamounts greater than 5% and preferably about 2575%. The solvent in suchconcentrate preferably has a distillation range of from about F. toabout 700 F. The organic solvents are hydrocarbon solvents, for example,petroleum fractions such as naphtha, kerosene, heater oil, and the like;aromatic hydrocarbons such as benzene, xylene, and toluene, orparaffinic hydrocarbons such as hexane, pentane, etc. The solventsemployed should, of course, be selected with regard to possiblebeneficial or adverse effects it may have on the final fuel oilcomposition. Thus, the solvent used should preferably burn withoutleaving an objectionable residue, and should be noncorrosive with regardto metals.

PREFERRED EMBODIMENT OF THE INVENTION The examples given below areillustrative of the preferred embodiment of the present invention. Ineach of the described examples, the ethylene-vinyl acetate copolymerhydrolyzed by alcoholysis or by saponification was a copolymer having anaverage molecular weight of about 2,400, and containing about 32% vinylacetate units.

The hydrolysis of the ethylene-vinyl acetate copolymer is illustrated bythe following examples:

EXAMPLE 1 Ethanol-Sodium Ethoxide Method 3,180 grams of 52%ethylene-vinyl acetate copolymer solution in kerosene was heated to C.and purged with nitrogen. The solution was then cooled to 78 C.,nitrogen purging discontinued, and the cooled solution treated with1,600 grams of absolute ethanol. The reaction mixture was heated toreflux temperature, ml. of a 1.0 N. sodium ethoxide in ethanol added andthe reaction mixture maintained at reflux temperature for one hour. Thereaction mass was then quenched with 10 ml. of glacial acetic acid, andthe mixture then stripped to 120 C. The recovered product as 61%hydrolyzed, that is 61% of the ester units of the ethylene-vinyl acetatecopolymer were hydrolyzed. The degree of hydrolysis was measured by gaschromatography (GC), which measures the amount of ethyl acetate formedas byproduct.

EXAMPLE II Ethanol-Sodium Methoxide Method 500 grams of a 60%ethylene-vinyl acetate copolymer solution in kerosene was heated to 120C. and purged with nitrogen to remove any moisture present. The solutionwas then cooled to 70 C., nitrogen purging stopped, and the cooledsolution treated with 55 grams of ethanol (denatured with benzene) andthe mixture heated to reflux temperature, i.e. about 82 C. The mixtureat reflux temperature was then treated with 7.9 ml. of 4.55 N sodiummethoxide in ethanol, and the reaction mixture maintained at refluxtemperature for one hour. The re action was then quenched with 2 ml. ofglacial acetic acid, and stripped of volatiles at 120 C. Gaschromatography analysis showed the recovered product to be 57%hydrolyzed.

EXAMPLE III Methanol-Sodium Methoxide Method 100 grams of a 52%ethylene-vinyl acetate copolymer solution in kerosene was heated to 120C. in a pressure reactor flask while purging with nitrogen to remove anymoisture. The solution was then cooled to 60 0., treated with 10 gramsof methanol and heated to 100 C.; the pressure in the reactor reachingabout 45 p.s.i. 7.5 ml. of sodium methoxide (1 N) was injected into thereaction mixture, and the mixture maintained at 100 C. for one hour. Thereaction was then quenched with 2 ml. of glacial acetic acid, cooled toroom temperature, the pressure-released, and the volatiles stripped offby heating to 120 C. The recovered product was 80% hydrolyzed.

" Saponification Method 300 grams of a 60% ethylene-vinyl acetatecopolymer solution in kerosene was heated to 100 C. The solution wasthen treated with 11 grams of sodium hydroxide dissolved in 30 ml.water, and the mixture maintained at reflux temperature (108-110 C.) forthree hours. The heated reaction mixture was then treated with 8 'ml. 12N HCl. The resultant acidic solution was heated to 150 C. to distill offthe water present in the product. The recovered product was 38%hydrolyzed.

EXAMPLE V Ethanol-Sodium Hydroxide Method 500 grams of a 60%ethylene-vinyl acetate copolymer solution in kerosene and 50 grams ofethanol were heated to reflux temperature. To the refluxing solution wasadded 50 ml. of 1 N NaOH and the mixture maintained at refluxtemperature for four hours. The solution was then treated with ml. of 12N HCl, and stripped of volatiles at 150 C. The removed product was 11%hydrolyzed.

The effectiveness of the hydrolyzed ethylene-vinyl acetate copolymer inimproving the pour and flowability or pumpability characteristics offuel oils and of crude oils is demonstrated by the data in the followingtables.

The effectiveness as pour depressors of the hydrolyzed ethylene-vinylacetate copolymer with varying degrees of hydrolysis, in concentrationsof 0.1%, in different resid fuel oils is demonstrated by the data inTable I.

TABLE I Degree of Pour point, F. hydrolysis, Sample number percentResid. A Resid. B Resid. C

The effectiveness of the hydrolyzed ethylene-vinyl acetate copolymerwith varying degrees of hydrolysis, in concentrations of 0.1%, asflowability or pumpability improvers in resid fuel oils is demonstratedby the data in Table II. These data were obtained by the method of theInstitute of Petroleum identified as IP 230 titled Pumpability Test forIndustrial Fuel Oils. Briefly, in this test a sample of the fuel oil,preheated if necessary, to a temperature not exceeding 180 F. to make itfluid, is poured into the cup of a Ferranti portable viscometer. This isimmersed in a bath at 180 F. for 20 minutes, and then transferred to abath at a predetermined temperature. After 15 minutes the viscometer isstarted at a rate of shear of 9.7 sec.- After a further 5 minutes thebath is cooled at 1 F./min. The temperature at which apparentviscosities of 6 poise and 25 poise are obtained are determined. Thistest gives the minimum storage and handling temperatures which wouldensure that the oil is usable in normal oil-fired installations.

TABLE II Resid. A, Resid. B, Degree of temperature, F. temperature, F.hydrolysis, Sample number percent 6 poise 25 poise 6 poise 25 poise Theeffectiveness of the hydrolyzed ethylene-vinyl acetate copolymer as pourpoint depressors in crude oils is shown by the data in the followingTable III.

TABLE III Pour point, F., crude oil Concena Hydrolysis, tration, BrutBrut Sample number percent percent Arzew Nigerian Control +16 -10 1 0.152 60 0 0.1 +16 -10 Percentages given herein and in the appended claimsare weight percentages unless otherwise stated.

Although the present invention has been described with reference tocertain specific preferred embodiments thereof, the invention is notlimited thereto, but includes withinits scope such modifications andvariations as some within the scope and spirit of the appended claims.

We claim:

1. Petroleum crude oil and fuel oil compositions having improved pourand flowability characteristics at low temperatures, comprising apetroleum oil of the group consisting of a crude oil and a fuel oilnormally having undesirable pour and flowability characteristics at lowtemperatures, and from about 0.001% to about 5% of a hydrolyzedcopolymer of ethylene and a vinyl ester of a lower alkyl fatty acidhaving up to about five carbon atoms, said copolymer having an averagemolecular weight of from about 500 to about 30,000, and containing about1090% ethylene and about l0% of said vinyl ester, said copolymer beinghydrolyzed to the extent of hydrolyzing from about 10% to about 90% ofthe ester units of said copolymer.

2. Petroleum crude oil and fuel oil compositions as described in Claim1, wherein the vinyl ester is vinyl acetate.

3. Petroleum crude oil and fuel oil compositions as described in Claim1, wherein the fuel oil is a residual fuel oil.

4. A petroleum fuel oil composition having improved pour and flowabilitycharacteristics, at low temperatures, comprising a major proportion of apetroleum fuel oil normally having undesirable pour and flowabilitycharacteristics at low temperatures and from about 0.0025 to about 1.0%of a hydrolyzed copolymer of ethylene and vinyl acetate, said copolymerhaving an average molecular weight of from about 700 to about 10,000,and containing about 6075% ethylene and about 40-25% vinyl acetate, saidcopolymer being hydrolyzed to the extent of hydrolyzing from about 30%to about 70% of the acetate units of said copolymer.

5. A fuel oil composition as described in Claim 4, wherein the petroleumfuel oil is a residual fuel oil.

6. A fuel oil composition as described in Claim 4, wherein the petroleumfuel oil is a distillate fuel oil.

7. A petroleum crude oil composition, comprising a major proportion of awaxy petroleum crude oil normally having undesirable flowabilitycharacteristics at low temperature, and from about 0.0025% to about 1.0%of a hydrolyzed copolymer of ethylene and vinyl acetate, said copolymerhaving an average molecular weight of from about 700 to about 10,000,and containing about 6075% ethylene and about 4025% vinyl acetate, saidcopolymer being hydrolyzed to the extent of hydrolyzing from about 30%to about 70% of the acetate units of said copolymer.

8. A concentrate composition for addition to petroleum crude oils andpetroleum fuel oils to improve the pour and flowability of such oils atlow temperatures, said concentrate comprising essentially a hydrocarbonsolvent boiling at a temperature in the range of from about F. to about700 F., and more than 5% of the hydrolyzed copolymer defined in Claim 1,said concentrate being capable of dilution with petroleum crude oils andwith petroleum fuel oils, normally having undersirable pour 7 8 andflowabiity characteristics at low temperatures, to pro- 3,560,461 2/1971 Y'onezu' et a1. 26087.3 duce crude oil and fuel oil compositionscontaining from 3,567,639 3/1971 Aaron et a1. 4462 about 0.001% to about5% of said hydrolyzed co- 3,776,247 3 C f r 'et a1. 4462 1 v 1 p0 ymerReferences Cited 5 PATRICK P. GARVIN, Primary Examiner i UNITED STATESPATENTS Y. H. SMITH, Assistant Examiner 3,344,129 9/1967 Bestian et a1260-873 CL "fwd 3,386,978 6/1968 Salyer 26087.3 44 70

1. PETROLEUM CRUDE OIL AND FUEL OIL COMPOSITIONS HAVING IMPROVED POURAND FLOWABILITY CHARACTERISTICS AT LOW TEMPERATURES, COMPRISING APETROLEUM OIL OF THE GROUP CONSISTING OF A CRUDE OIL AND A FUEL OILNORMALLY HAVING UNDESIRABLE POUR AND FLOWABILITY CHARACTERISTICS AT LOWTEMPERATURE, AND FROM ABOUT 0.001% TO ABOUT 5% OF A HYDROLYZED COPOLYMEROF ETHYLENE AND A VINYL ESTER OF A LOWER ALKYL FATTY ACID HAVING UP TOFIVE CARBON ATOMS, SAID COPOLYMER HAVING AN AVERAGE MOLECULAR WEIGHT OFFROM ABOUT 500 TO ABOUT 30,000, AND CONTAINING ABOUT 10-90% ETHYLENE ANDABOUT 90-10% OF SAID VINYL ESTER, SAID COPOLYMER BEING HYDROLYZED TO THEEXTEND OFF HYDROLYZING FROM ABOUT 10% TO ABOUT 90% OF THE ESTER UNITS OFSAID COPOLYMER.